If you want to disable all WordPress comments on all future articles by default, you can go to Settings → Discussion and deselect "Allow people to post comments on new articles". You can enable comments on future articles. This just disables them by default so you don’t have to always perform that extra step.
When editing a Page or Post in WordPress, you can enable or disable comments from the Discussion meta box.
If you don’t see the Discussion meta box in your control panel, 1.) click the "Screen Options" dropdown at the top right of your screen and 2.) make sure "Discussion" is checked.
If you’ve got a bunch of Pages or Posts that you want comments disabled on, you can view all your Pages or Posts list by clicking Pages or Posts respectively. 1.) Click the "Quick Edit" link and 2.) check/uncheck "Allow Comments" then 3.) click "Update" to save the settings.